Sexual Reproduction in Plants

12 Key excerpts on "Sexual Reproduction in Plants"

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  Embryology of Plants

  • Rajesh Singh(Author)
  • 2020(Publication Date)
  • Delve Publishing

    (Publisher)

  Similarly, the vegetative method has different sub -methods like cutting, budding, layering, separating, and grafting which are being used for producing the new plant which is similar to their parent plant. The sexual reproduction process takes place through pollination. Pollination is a process known as the sexual process which is used by the plants for reproduction. In this method, there is an involvement of male and female gametes that fuses together to form a new plant through an embryo. There are typically two types of pollination methods like self-pollination and cross-pollination which is being explained in detail. 2.1. INTRODUCTION Reproduction is a process that takes place in order to produce the new offspring in the plants. Therefore, the reproduction process is required for the generation of new individuals. Plants that are present on the land are considered to have asexual reproduction process, where the offspring are found to be genetically identical to their parents or sexual by creating a genetic variation. The life cycle of the plants basically involves two alternating generations: sporophytes that are making the spores and the gametophyte that is producing the make and the female gametes. During the evolution in the land plant, the life cycle has been altered from the gametophyte generation. It is observed that the structure that is making the gametes and spores, and the way through which the reproductive cells are being exchanged and dispersed. It also becomes altered, as the plants become to adapt the living in the drier environments. Flowers are representing the reproductive organ of the flowering plants and considered to be very important for the identification as it is typically providing the characters that are steadily being expressed within a taxon. Plant Reproduction 31 This is because the floral characteristics are basically under strong genetic control and it is not affected by the changes in the environments.

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  Plant Propagation Concepts and Laboratory Exercises

  • Caula A. Beyl, Robert N. Trigiano, Caula A. Beyl, Robert N. Trigiano(Authors)
  • 2016(Publication Date)
  • CRC Press

    (Publisher)

  • Mutation breeding and biotechnology can be used to breed new cultivars from clonal material without sexual reproduction. 66 Timothy A. Rinehart, Robert N. Trigiano, Phillip A. Wadl, and Haley S. Smith thousands upon thousands of exact genetic copies of ‘Cherokee Sunset.’ In the end, the consumer receives the desired product with the expected characteristics. Other horticultural plants, especially many bedding species and vegetable crops, are propagated mainly by seeds. This is a sexual process that entails meiosis in both the male and the female cells to form haploid gametes. The original diploid number of the chromosome is restored by the fusion of the haploid gametes from each parent. As will be discussed below in more detail, sexual reproduction in angiosperms involves pollination, in which the pollen or the male gametophyte lands on receptive female sur-faces, usually the stigma of the ovary. Eventually, a pro-cess called “double fertilization” takes place, in which one male sperm nucleus fuses with the female egg to create the zygote and another sperm nucleus fuses with two other nuclei of the female gametophyte to form the primary endosperm nucleus. The result of sexual reproduction is a seed containing an embryo and everything necessary to grow a new seedling. ALTERNATION OF GENERATIONS The concept of alternation of generations is central to understanding sexual reproduction in angiosperms as well as most other organisms. In this case, generations do not refer to parents and children, but rather to the nuclear condition or the ploidy number of the plant’s cells during the life cycle of the plant. Ploidy level is the number of copies of chromosomes in the nucleus.

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  Principles of Plant Genetics and Breeding

  • George Acquaah(Author)
  • 2012(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  gametes . Gametes are products of meiosis and, consequently, seeds are genetically variable. Asexual or vegetative reproduction mode entails the use of any vegetative part of the plant for propagation. Some plants produce modified parts, such as creeping stems (stolons or rhizomes), bulbs or corms, which are used for their propagation. Asexual reproduction is also applied to the condition whereby seed is produced without fusion of gametes (called apomixis). It should be pointed out that some plants could be reproduced by either the sexual or asexual mode. However, for either ease of propagation or for product quality, one mode of reproduction, often the vegetative mode, is preferred. Such is the case in flowering species such as potato (propagated by tubers or stem cuttings) and sugarcane (propagated by stem cuttings).

  5.4 Sexual Reproduction

  Sexual reproduction increases genetic diversity through the involvement of meiosis. Flowering plants dominate the terrestrial species. Flowering plants may reproduce sexually or asexually.

  5.4.1 Sexual Lifecycle of a Plant (Alternation of Generation)

  The normal sexual lifecycle of a flowering plant may be simply described as consisting of events from first establishment to death (from seed to seed in seed-bearing species). A flowering plant goes through two basic growth phases – vegetative and reproductive , the former preceding the latter. In the vegetative phase, the plant produces vegetative growth only (stem, branches, leaves, etc., as applicable). In the reproductive phase, flowers are produced. In some species, exposure to a certain environmental factor (e.g., temperature, photoperiod) is required to switch from the vegetative to the reproductive phase. The duration between phases varies among species and can be manipulated by modifying the growing environment.

  For sexual reproduction to occur, two processes must occur in sexually reproducing species. The first process, meiosis, reduces the chromosome number of the diploid (2n ) cell to the haploid (n ) number. The second process, fertilization, unites the nuclei of two gametes, each with the haploid number of chromosomes, to form a diploid. In most plants, these processes divide the lifecycle of the plant into two distinct phases or generations, between which the plant alternates (called alternation of generation ) (Figure 5.1 ). The first phase or generation, called the gametophyte generation , begins with a haploid spore produced by meiosis. Cells derived from the gametophyte by mitosis are haploid. The multicellular gametophyte produces gametes by mitosis. The sexual reproductive process unites the gametes to produce a zygote that begins the diploid sporophyte generation

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  Advanced Plant Production NQF4 SB

  TVET FIRST

  • W Burger(Author)
  • 2013(Publication Date)
  • Macmillan

    (Publisher)

  A gamete is produced by meiosis, which is a special kind of cell division that produces cells with half the number of genes (called n) found in the cells that make up the rest of the plant or animal body. When the sex cells fuse during fertilisation they form a zygote with the correct number of genes for that species (called 2n). The zygote develops into an adult plant or animal Sexual reproduction in flowering plants involves the following important steps: • The production of gametes: The male gamete is enclosed in the pollen produced at the end of the stamens in the pollen sacs; and the female gamete is enclosed in the ovule produced in the ovary of the flower. • Pollination: This occurs when a ripe pollen grain reaches a ripe stigma. • Fertilisation: This occurs when the pollen tube that grows down the style enters the ovule and the nuclei of the male and female gametes fuse. Section 1.2.5 on page 12 shows you how this takes place. 8 Module 1 • Fruit and seed development: The fertilised ovule develops into the seed and the ovary develops into the fruit. • Seed dispersal: Seed are dispersed (carried away from the parent plant) by wind, water and animals. The advantage of dispersal is that the new seedlings do not grow too close to the parent plants and therefore do not compete for resources such as soil, water, soil nutrients and sunlight. • Seed germination: When a seed is dispersed and lands in an area that is favourable for growth, the seed will germinate and a new seedling will grow. If this seedling grows to adulthood and takes part in sexual reproduction again, then we can say the sexual reproductive cycle has been completed. 1.2.2 Pollination Pollination is the process whereby a ripe pollen grain reaches a ripe stigma of the same flower or of another flower on the same plant or on another plant of the same species.

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  Principles of Horticulture: Level 3

  • Charles Adams, Mike Early, Jane Brook, Katherine Bamford(Authors)
  • 2015(Publication Date)
  • Routledge

    (Publisher)

  4    

  CHAPTER

  Level 3

  Plant reproduction

  Figure 4.1 Bees and other pollinating insects are attracted to large, colourful fl owers. The Iris shown has blue fl owers, a colour attractive to bumble bees, and tepals which can support the bee’s weight with nectar guides directing the bees towards nectaries at their base

  This chapter includes the following topics:

  • Inflorescence types

  • Pollination syndromes

  • Cross- and self-pollination mechanisms

  • The relevance of cross-and self-pollination to horticulture

  • Fertilization

  • Seed structure – endospermic and non-endospermic seeds

  • Seed dormancy

  • Seed quality – testing and treatments

  • Seed provenance and conservation

  • Fruit development, structure and classification

  • Asexual reproduction and vegetative propagation

  Principles of Horticulture. 978-0-415-85909-7 © C.R. Adams, M.P. Early, J.E. Brook and K.M. Bamford. Published by Taylor & Francis. All rights reserved.

  Figure 4.2 Inflorescences which are designed to maximize pollen dispersal and capture: (a) in a Betula (birch) left, female catkins; right, male catkins; (b) in grasses

  Reproduction is the process by which new individuals are formed and hence the species is perpetuated. In plants this can be asexual, by means of a range of vegetative structures or it can be sexual resulting in seeds. Sexual reproduction has two key advantages for the plant. It gives rise to variation in a plant's offspring, enabling it to withstand environmental pressures and it also provides the means by which plants can colonize new areas, through dispersal of seeds, often enclosed within a fruit. Although plants produced from seed are genetically variable and will not be uniform in their growth and other characteristics such as size, flower colour etc., this variation can be controlled by skilled plant breeders (see F1 hybrids p. 47

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  Botany For Dummies

  • Rene Fester Kratz(Author)
  • 2011(Publication Date)
  • For Dummies

    (Publisher)

  along the edges. These plantlets can drop to the ground, produce roots, and grow into new individuals. Plants called liverworts make tiny little cups called gemmae on the surfaces of their leaf-like bodies. When rain splashes into the cups, clumps of cells break off and scatter, forming new plants wherever they land.

  Flowers: Although flowers usually mean sexual reproduction, some plants, such as citrus trees, produce seeds asexually by a process called agamospermys . During agamospermy, a cell from the parent plant develops into a seed containing an embryo that is a genetic copy of the parent.

  Fragmentation, the process where a plant part breaks off and develops into a new individual, occurs with stems, roots, and even leaves.

  Sexual reproduction

  Although asexual reproduction is very common in plants, most plants can also mix it up a little by combining their genetic information with another plant to produce offspring that have unique combinations of genetic information.

  Most plants can do asexual reproduction and sexual reproduction

  , where an egg from one plant combines with sperm from another plant to produce offspring that have new combinations of traits. Tulips, for example, reproduce asexually through tulip bulbs, but also reproduce sexually by making flowers, fruits, and seeds.

  The most obvious participants in sexual reproduction are the flowering plants — their showy flowers are basically advertising that they’re looking for a mate — but more subtle plant sex is happening around you all the time. All the cone-bearing plants, such as pine, spruce, and fir, do sexual reproduction, as do flowering trees like maple, oak, and willow. Sex is even going on among the grass and moss under your feet!

  Comparing reproductive styles Both asexual reproduction and sexual reproduction have their advantages:

  Asexual reproduction rapidly produces copies of a successful organism.

  • Advantage:

  If the traits of the parent plant are working well in a particular environment, then asexual reproduction will produce more successful organisms without the hassle of finding a mate. In other words, if it ain’t broke, don’t fix it.

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  Manual on Vegetable Breeding

  • Singh, Pradeep Kumar(Authors)
  • 2021(Publication Date)
  • Daya Publishing House

    (Publisher)

  There are finer differences in these types. For example, there may be differences between the time of pollen shed and stigma receptivity. This ebook is exclusively for this university only. Cannot be resold/distributed. 3. Self-fertilization versus cross-fertilization: Just because a flower is successfully pollinated does not necessarily mean fertilization will occur. The mechanism of self-incompatibility causes some species to reject pollen from their own flowers, thereby promoting out crossing. 4. Sexuality versus asexuality: Sexually reproducing species are capable of providing seed through sexual means. Asexuality manifests in one of two ways – Vegetative reproduction (in which no seed is produced) Or Agamospermy (in which seed is produced). TYPES OF REPRODUCTION Plants are generally classified into two groups based on mode of reproduction as either sexually reproducing or asexually reproducing. Sexually reproducing plants produce seed as the primary propagules. Seed is produced after sexual union (fertilization) involving the fusion of sex cells or gametes. Gametes are products of meiosis and, consequently, seeds are genetically variable. Asexual or vegetative reproduction mode entails the use of any vegetative part of the plant for propagation. Some plants produce modified parts such as creeping stems (stolons or rhizomes), bulbs, or corms, which are used for their propagation. Asexual reproduction is also applied to the condition whereby seed is produced without fusion of gametes (called apomixis). It should be pointed out that some plants can reproduce by either the sexual or asexual mode. However, for ease of either propagation or product quality, one mode of reproduction, often the vegetative mode, is preferred. Such is the case in flowering species such as potato (propagated by tubers or stem cuttings) and sugarcane (propagated by stem cuttings).

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  Essentials of Plant Breeding

  • Emea, N(Authors)
  • 2018(Publication Date)
  • Agri Horti Press

    (Publisher)

  This ebook is exclusively for this university only. Cannot be resold/distributed. Plant Reproduction 211 DIAGRAM OF A DICOT PLANT One of the simplest methods of reproduction is when one cell divides and becomes two equal halves that will grow large enough to split again. With plants and animals that reproduce this way, each generation is identical to the one before. CELL DIVIDING DIAGRAM WITH ONE PARENT CELL Plant reproduction may be sexual, in which two parents produce a genetically different individual; or asexual, involving the propagation of plants that are genetically identical to the parent. THE SEXUAL PLANT LIFE CYCLE Sexual reproduction is important in providing genetic variability. All plants that reproduce sexually must go through meiosis. Meiosis is a unique kind of cell division during which the paired sets of chromosomes present in sexually mature plants, called sporophytes, are halved. Because they have the two sets of chromosomes, one from the male parent and the other from the female, the cells of sporophytes are called diploid . During this process, pairs of homologous, or identical, chromosomes, one from each parent, line up together. Crossing-over, or the exchange of genetic material between these homologous chromosomes, may occur at this time. Crossing-over is critical for producing some of the genetic variability in resulting offspring. Meiosis typically produces four haploid cells, each with one set of chromosomes, from a single diploid cell. These haploid cells become gametes-eggs and sperm. Without meiosis, sexually reproducing organisms would not have a mechanism for reducing the total chromosome number by half so that genetic variability can be introduced via crossing-over. Meiosis is a critical step that must occur prior to the fusion of sperm and egg, which restores the diploid chromosome number. Alternating Generations Plants undergo a two-phase cycle of sexual reproduction This ebook is exclusively for this university only.

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  Physiology and Behaviour of Plants

  • Peter Scott(Author)
  • 2013(Publication Date)
  • Wiley-Interscience

    (Publisher)

  Longevity . Plants may, in many instances, be long-suffering and long-lasting, but if the great extinctions of the past teach us anything, it is that nothing lasts forever. No matter how old an individual plant is, one day conditions will change to make survival impossible. Plants need some means of surviving such adverse conditions, which may be local or temporary, and reproduction can offer a solution to this. Clonal plants may move away from the point of origin of the mother plant and therefore widen the spread of the plant, thereby escaping a particular stress. In addition, seeds offer even greater opportunities to disperse genetic material well away from the parent plant and also provide a structure that can remain dormant over prolonged periods. This permits a plant to survive temporary changes in conditions. Clones or seeds also produce new individuals which are free from fungal infections or damage present in the parent plant.

  3. Genetic variation . Finally, reproduction offers opportunities for genetic variation, which is essential in a changing habitat. Asexual reproduction offers little opportunity for genetic variation but the potential from sexual reproduction is immense.

  In this chapter we will look in greater detail at how plants reproduce and the merits and limitations of the different methods.

  Asexual reproduction

  Many plant species use asexual reproduction as a means of propagation. Asexual reproduction has several advantages and disadvantages (Figure 9.1 ). This form of reproduction produces individuals that are genetically identical and does not support much scope for phenotypic variation. This can lead to plants being vulnerable to changes in the habitat. In addition, offspring are generated close to the parent plant, so parent and offspring often have to compete for nutrients and light. However, asexually produced plants usually attain adulthood in advance of seedlings of the same parent and hence rapidly out-compete neighbouring plants reliant on seeds. Under many conditions, asexual reproduction is more successful than sexual reproduction for plants and a large number of species use this as their sole means of reproduction.

  Figure 9.1 ASexual Reproduction in Plants. Plants possess a range of different means of asexual reproduction. (A) Apomixis: using this method, the flowers spontaneously produce seeds without the need for any fertilization. The actual source of the embryo can come from the egg cell or the cells surrounding it. (B) A hyacinth bulb (Hyacinthus hybrid); bulbs frequently produce bulbils (small offset bulbs) at the base of the bulb. (C) A gladiolus corm (Gladiolus hybrid); corms frequently produce small offset corms at the base of the stem. (D) Strawberry plant (Fraxinus hybrid), forming runners, modified stems that form new plants. (E) Black poplar (Populus nigra

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  Apomixis in Plants

  • Sven Asker, Lenn Jerling(Authors)
  • 2017(Publication Date)
  • Routledge

    (Publisher)

  This scenario fits with the theory of POL where the basic factor is to survive (DNA repair), and second, to produce new automata which are capable of functioning (as proven by the parent). The genetic variation (fertilization in combination with meiosis) is a secondarily derived tactic to meet environmental fluctuations.

  2. Clones vs. Clades — Arguments for Sexual Reproduction Based on Speciation Rates

  A historical explanation for the prevalence of sexual reproduction emphasizes the role of the rate of speciation.38 The view that major evolutionary changes occur at speciation events and not during the course of intraspecific gradual evolution is held within the theory of punctuated equilibria.12 The function of sexual reproduction is not to increase the evolutionary rate within a species and lower the rate of extinction, but rather the long-term advantage lies in higher rates of diversification.38

  Stebbins41 claimed that asexual groups tend to become extinct rapidly, not because of their inability to evolve, but because of a poor ability to diversify. Asexual clones may even tend to survive longer than sexuals since clones may diversify more rapidly intraspecifically in an ecological and genetic sense because they are not constrained by interbreeding.38 Large-scale evolution is, according to Stanley,39 decoupled from microevolution and large-scale trends are determined by the ability to speciate. Species selection favors those which survive for long periods and speciate at a high rate. This view falls within the framework of POL, but not directly within neo-Darwinism, since it emphasizes the persistence aspect of lineages and selection above the species level. The reason for sex is thus that extinction rates can be balanced by high speciation rates.39

  3. Sex as a Consequence of the Level of Organization

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  Biological Approaches and Evolutionary Trends in Plants

  • Shoichi Kawano(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Reproductive success can be calculated for an individual according to the formula QRS l = QEFFt • p MI or QEFFi • a M i where QEFFi = female reproductive efficiency of an individual PMI = establishment percentage of daughter ramets produced by a given mother individual a MI = germination percentage of vegetative propagules produced by a given mother individual. For a population, female reproductive success QRSp can be expressed as fol-lows QRSp = QEFFp • p M P or QEFFp • cc MP where QEFFp = female reproductive efficiency of a given population PMP = establishment percentage of daughter ramets produced within this population a MP = germination percentage of vegetative propagules produced within this population. The general evaluation sequence is QEFF -» QRS. VI. Some Biological Features of Sexual and Asexual Reproduction in the Angiosperms As far as population biology and/or ecology is concerned, sexually and asexually reproducing Angiosperms closely resemble each other in numerous aspects. I pro-pose to compare briefly some important features. 288 K. M. Urbanska A. Reproductive output While both the general morphology of reproductive units and the potential repro-ductive output are primarily determined by genetic factors, the actual number of seeds, specialized vegetative propagules, or daughter ramets apparently remain at least partially under environmental influence. Ecological factors operate both di-rectly via the condition of the mother plant related to the availability of nutrients and other resources, and indirectiy via meteorological conditions occurring during the propagule maturation period (for reproduction by seed, see Urbanska and Schiitz, 1986). Agamospermous plants behave in this respect like the sexual taxa, seeds de-veloped in less extreme conditions being fuller and germinating much better than those originating from extreme and unpredictable environment (Schiitz, 1988, 1989; Urbanska and Schiitz, 1986).

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  Cambridge O Level Biology 5090

  • Azhar ul Haque Sario(Author)
  • 2023(Publication Date)
  • tredition

    (Publisher)

  Genetic Potluck Party: Cross-pollination is like plants sharing their genetic gifts at a big party. Pollen from one plant fertilizes another, leading to babies with a mix of features. This genetic diversity gives these plants a bigger set of traits to work with, like having a full wardrobe for all seasons.

  Ready for Surprises: Plants that cross-pollinate are better at dealing with unexpected changes. They have a wide variety of genetic traits, so there's a better chance some of them will cope with new diseases or environmental shifts. It's like having a tool for every job that might come up.

  Relying on Pollinator Buddies: These plants depend on friends like bees and birds to move pollen. They have a special relationship with these pollinators, but if their pollinator pals are in trouble, so are they. It's like needing a friend to lend you a tool – if they don't show up, you're stuck.

  In Summary:

  Both self-pollination and cross-pollination have their ups and downs. Self-pollination offers simplicity and independence but limits genetic variety and adaptability. Cross-pollination brings a rich mix of genes, which is great for adapting to new situations, but it also means these plants need pollinators to thrive. How a plant reproduces is a big deal, influencing how it deals with life's challenges and opportunities.

  In the intricate journey of plant reproduction, the growth of the pollen tube and its subsequent entry into the ovule, leading to fertilization, is a fascinating process. This natural event is key to the development of seeds in flowering plants. Let's explore this process in simple, yet detailed terms.

  1. The Pollen Grain's Arrival: The story begins when a pollen grain, the male reproductive unit of a flower, lands on the stigma of a pistil – the female part of another flower. The stigma is often sticky, helping the pollen grain to adhere.

  2. Germination of the Pollen Grain: Once securely positioned, the pollen grain undergoes a transformation. It germinates, which means it starts to grow. This growth is fueled by the nutrients present in the pollen.

  3. Formation of the Pollen Tube: The germinated pollen grain forms a thin, tubular structure called the pollen tube. This tube is like a microscopic tunnel, and it has a crucial mission: to transport the male genetic material to the female ovule.

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